1. Field of the Invention
The present invention relates generally to the measurement of displacement and, more particularly, to mechanical amplifier systems and methods for measuring displacement. Such systems and methods may also be applicable to load monitoring systems and methods.
2. Description of Related Art
Monitoring of the load in load carrying members is very important in some applications. One load monitoring device uses variable reluctance sensors to measure the displacement in the direction of the applied load. The applied load is obtained by multiplying the displacement by the stiffness of the load carrying member. The precision of the measurement as a percentage of full scale load is determined by the ratio of the smallest displacement that the device can resolve to the displacement under full load.
The elements of such load monitoring devices typically include a load carrying member, a displacement measurement device (e.g., a sensor) with associated processing, and a mechanism for attaching the sensor to the load carrying member. The device measures the deformation of the load carrying member over a specific distance customarily referred to as the gauge length. The deformation of the load carrying member under load is directly proportional to this gauge length.
One application of load monitoring systems is in connection with moorings and risers in offshore oil production platforms. One such monitoring system includes a load monitoring device composed of a load measurement unit (LMU) that includes variable reluctance sensors attached to two rings around the periphery of a load carrying member to measure the load associated with that member. The LMU measures load based on the displacement between the two rings of sensors.
With a sufficient number of sensors, the LMU can measure load, bending, and orientation of bending. Due to limitations typically associated with displacement sensors, the gauge length of the LMU needs to be long to provide sufficient displacement to accurately measure these load-related features. For example, the gauge length of the LMU may be in the order of 36, 48, or 60 inches.
In some situations, it is important to reduce the gauge length of the devices. As a result, there is a need in the art for mechanisms to reduce the gauge length while maintaining the precision.